MK50H25(1994) 데이터 시트보기 (PDF) - STMicroelectronics
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MK50H25 Datasheet PDF : 64 Pages
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MK50H25
4.1.2 Control and Status Register Definition
4.1.2.1 Control and Status Register 0 (CSR0)
RAP<3:1> = 0
1111110000000000
5432109876543210
P
T
S
T
D
D
T
X
R
X
I
N
I
N
M
E
M
I
R
T
P
I
T
I
R
I
DO
M
D
P
T
X
R
X
O
N
O
N
E
A
T
R
R
R
S
S
O
R
U
R
N
T
N
T
N
T
0
BIT NAME
15 TDMD
14 STOP
13 DTX
12 DRX
11 TXON
10 RXON
16/64
DESCRIPTION
TRANSMIT DEMAND, when set, causes the MK50H25 access the
Transmit Descriptor Ring without waiting for the Transmit poll time in-
terval to lapse. TDMD need not be set to transmit a frame, it merely
hastens the MK50H25’s response to a Transmit Descriptor Ring entry
insertion by the host. TDMD is written with ONE ONLY and cleared by
the MK50H25 microcode after it is used. It may read as a ”1” for a
short time after it is written because the microcode may have been
busy when TDMD was set. It is also cleared by Bus RESET. Writing a
”0” in this bit has no effect.
STOP, when set, indicates that MK50H25 is operating in the Stopped
phase of operation. All external activity is disabled and internal logic is
reset. MK50H25 remains inactive except for primitive processing until
a START primitive is issued. STOP IS READ ONLY and set by Bus
RESET or a STOP primitive. Writing to this bit has no effect.
Disable Transmitter ring prevents the MK50H25 from further access to
the Transmitter Descriptor Ring. No transmissions are attempted after
finishing transmission of any frame in transmission at the time of DTX
being set. TXON acknowledges changes to DTX, see below. DTX is
READ/WRITE.
Disable the Receiver prevents the MK50H25 from further access to the
Receiver Descriptor Ring. No received frames are accepted after fin-
ishing reception of any frame in reception at the time of DRX being set.
If DRX is set while a data link is established, the MK50H25 will go into
the Local Busy state and will send an RNR response frame to the re-
mote station. Upon clearing DRX the MK50H25 will send a RR re-
sponse frame. RXON acknowledges changes to DRX, see description
of RXON. DRX is READ/WRITE.
TRANSMITTER ON indicates that the transmit ring access is enabled.
TXON is set as the Start primitive is issued if the DTX bit is ”0” or after-
ward as DTX is cleared. TXON is cleared upon recognition of DTX be-
ing set, by sending a Stop primitive in CSR1, or by a Bus RESET. If
TXON is clear, the host may modify the Transmit Descriptor Ring en-
tries regardless of the state of the OWNA bits. TXON is READ ONLY;
writing to this bit has no effect.
RECEIVER ON indicates that the receive ring access is enabled.
RXON is set as the Start primitive is issued if the DRX bit is ”0” or after-
ward as DRX is cleared. RXON is cleared upon recognition of DRX
being set, by sending a Stop primitive in CSR1, or by a Bus RESET. If
RXON is clear, the host may modify the Receive Descriptor Ring en-
tries regardless of the state of the OWNA bits. RXON is READ ONLY;
writing to this bit has no effect.
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